1. Field of the invention
The present invention relates in general to Ophthalmic instruments and equipment and in particular to Ophthalmic instrument support stands.
2. Prior art
In the examination of patients by Ophthalmologist, Optometrists, and other eye care professionals, there is a need to bring various instruments into position directly in line with the patient's field of vision and to move such instruments, upon completion of their role in a particular phase of examination, to a position that is out of the way of patient and examiner. Instruments of examination include but, are not limited to, slit lamps, the, tonometers, and refractometer. These instruments employ a high degree of precision in manufacture and use which makes them relatively heavy while requiring a very stable platform for accurate operation.
In the past, stands with counterbalanced arms for the delivery of instrument platforms have been devised. In these type devices, the practice has been to distribute the weight in a single suspension vertical configuration which requires a large, heavy base to prevent the stand from overturning when the support arm is extended while bearing the weight of an instrument. Such a configuration has set limits on the horizontal extension of these stands in a position directly beside the patient chair. This placement interferes with the necessary access to the area directly beside the patient during the course of examination.
Another restriction imposed by the generally vertical orientation of prior designs is a limit of downward vertical movement of the instrument support arm in such devices. Such restriction prohibits the examination of wheel chair bound patients without moving them from their chairs into the patient chair because of the lower sitting level of the wheelchair. Moving such patients is difficult and potentially dangerous for both patient and examiner.
Due to the mandatory lateral positioning of prior stands, the instrument support arm approaches the patient's legs in a perpendicular manner also limiting downward movement of the arm and allowing for the possibility of injury in accidental arm decent.
Prior designs also provide locking mechanisms which prevent upward as well as downward movement of the instrument support arm. Preventing upward movement allows for the possibility of trapping an unattended patient who may be unfamiliar with the operation of lock switches and instrument support arm operation.